Buying gas for a trip

Buy a couple of gas cans the next time you travel far.
Call your friends/family before making a trip, and ask them to check prices before you go, so you know which area is cheaper. Look for a steady increase or decrease during trips: you'll find out where prices are lower. (Watch signs along highways/freeways.)
If travelling to a cheaper area, buy just enough at home to get you there. Before you leave your destination, fill up and top off all your tanks, and fill all your gas cans. If you stop on the way home, top it off again. When you get home, use up all the gas you bought before buying locally again.
Reversely, if traveling to a more expensive area, fill up tanks and cans at home before traveling, and try to limit gas usage at your destination as much as possible. Use up tanks and cans before buying gas there. The goal is to never have to purchase gas at the higher price.

-----------Civilization stands on the willingness of those who back up it's principles with more than words. --Alan Dean Foster